JPH11312498A - Flat fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat fluorescent lamp that can perform uniform surface light emission even if luminance is lowered. SOLUTION: In this fluorescent lamp, a phosphor film 3 is formed on the surface of a front glass board 1 facing the discharge space S, a transparent front electrode 4 is formed on its outside surface, a phosphor film 5 similar to the aforementioned one is formed on the surface of a rear glass board 2 facing the discharge space S, a rear electrodes 6 made of molybdenum is formed on its outside surface, and an A.C. pulse voltage is applied to the front electrode 4 and the rear electrodes 6 through lead terminals 7. A gas having a mixing ratio of 20%, of Xe and 80% of Ar is so enclosed in the discharge space S as to set the total pressure to 66 kPa. Then, when the thickness (X) of the front glass board 1 and the rear glass board 2 is varied within the range of 1.0 mm-3.5 mm and a gas charging pressure (P) is also varied, uniform surface light emission can be provided as long as a condition of 1.6 logX+5.9×10<4> <=P<=1.6 logX+11.5×10<4> is satisfied even if luminance is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat fluorescent lamp used as a backlight of a liquid crystal display device in addition to an ordinary lighting device.

[0002]

2. Description of the Related Art Conventional flat fluorescent lamps are disclosed in
One disclosed in Japanese Patent No. 87869 is known. The flat-type fluorescent lamp disclosed in this publication is configured such that an airtight discharge space is formed inside by joining a front glass substrate and a rear glass substrate through a sealing member around the front glass substrate and the rear glass substrate. A phosphor film is formed on the surface on the discharge space side, a transparent front electrode is formed on the outer surface of the front glass substrate, and a rear electrode is formed on the outer surface of the rear glass substrate. By applying an AC pulse voltage to the substrate, a micro-discharge is generated over the entire discharge space via the front glass substrate and the back glass substrate, which are dielectrics, and the micro-discharge is enclosed in the discharge space. The gas is excited to generate ultraviolet rays, and the ultraviolet rays excite and emit the phosphor.

In the above prior art, in order to perform stable and uniform surface emission, the pressure of the gas sealed in the discharge space and the height of the discharge space (the distance between the front glass substrate and the back glass substrate) ) Satisfy a certain relationship.

[0004]

When a flat fluorescent lamp is used, for example, as a backlight for a meter for a car or a display device for a car navigation system, the brightness of the backlight is greatly increased when the surroundings are dark at night or the like. Need to be reduced. However, when the brightness is reduced in the above-mentioned conventional flat fluorescent lamp, the light emitting spot moves, so-called flickering occurs, and uniform surface light emission is not achieved. In addition, the reactive current increases, and efficient light emission is not performed.

[0005]

Means for Solving the Problems The inventors of the present invention pay attention to the relationship between the filling gas pressure and the dielectric film thickness in order to stably and uniformly emit light even when the luminance is reduced. And
Second, the present invention has been made by focusing on the surface shape forming the discharge space.

That is, in order to solve the above-mentioned problems, the invention according to claim 1 of the present application, which focuses on the relationship between the gas pressure and the film thickness of the dielectric material, has a structure in which the front glass substrate and the rear glass substrate are joined together. In a flat fluorescent lamp in which an airtight discharge space is formed, a phosphor film is formed on inner surfaces of the front glass substrate and the rear glass substrate, and a transparent front electrode is formed on an outer surface of the front glass substrate, A back electrode is formed on the outer surface of the back glass substrate. Further, when the gas pressure of the discharge space is P (Pa) and the thickness of the glass substrate is X (mm), the following equations (1) and ( A configuration satisfying 2) was adopted. 1.0 ≦ X ≦ 3.5 (1) (1.6logX + 5.9) × 10 ⁴ ≦ P ≦ (1.6logX + 11.5) × 10 ⁴ (2) In the present invention, the glass substrate functions as a dielectric.

According to a second aspect of the present invention, there is provided a flat-type fluorescent lamp in which an airtight discharge space is formed in a state where the front glass substrate and the rear glass substrate are joined together, wherein the inner surface of the front glass substrate is provided. A transparent front electrode, a dielectric film and a phosphor film are sequentially formed on the rear glass substrate, and a back electrode, a dielectric film and a phosphor film are sequentially formed on the inner surface of the rear glass substrate. Fill gas pressure is P (Pa),
When the thickness of the dielectric film is Y (mm), the following equation (3)
A flat fluorescent lamp characterized by satisfying (4). 10 × 10 ⁻³ ≦ Y ≦ 1.3 ・ ・ ・ ・ ・ ・ ・ ・ ・ (3) (1.6logY + 5.9) × 10 ⁴ ≦ P ≦ (1.6logY + 11.5) × 10 ⁴・ ・ ・ ・ ・ (4)

According to a third aspect of the present invention, there is provided a flat-type fluorescent lamp in which an airtight discharge space is formed in a state where the front glass substrate and the rear glass substrate are joined together. A phosphor film is directly formed on the inner surface of one of the glass substrates and electrodes are formed on the outer surface, and the inner surface of the other glass substrate of the front glass substrate or the back glass substrate is formed on the inner surface of the other glass substrate. The electrode, the dielectric film, and the phosphor film are sequentially formed. Further, the pressure of the gas in the discharge space is P (Pa), the thickness of one glass substrate is X (mm), and the thickness of the dielectric film is Y ( mm)
Wherein the following formulas (5) to (7) are satisfied. 1.0 ≦ X ≦ 3.5 (5) 10 × 10 ^-3 ≦ Y ≦ 1.3・ ・ ・ ・ ・ ・ ・ (6) (1.6logY + 5.9) × 10 ⁴ ≦ P ≦ (1.6logX + 11.5) × 10 ⁴・ ・ ・ ・ ・ (7)

As specified in the above formula (1), the reason why the thickness (X) of the glass substrate as a dielectric is 1.0 ≦ X ≦ 3.5 (mm) is that the glass substrate having a thickness of less than 1.0 mm has sufficient strength. When the thickness exceeds 3.5 mm, the accumulation of electric charges becomes excessive and the discharge to the surroundings increases, so that not only the reactive power increases sharply but also the weight increases, and the thickness (Y) of the dielectric film becomes 10 ×. Ten
^-3 ≦ X ≦ 1.3 (mm) is 10 × 10 ⁻³ (0.01 mm)
If it is less than 1, the dielectric film becomes too thin, the amount of accumulated charge is insufficient, it is difficult to satisfy the function of the dielectric discharge, and there is a possibility that the dielectric breakdown will occur over time, on the other hand, exceeds 1.3 mm Then, the accumulation of electric charges becomes excessive, the emission to the surroundings increases, and the reactive power increases rapidly. Therefore, the thickness (X) of the dielectric film (glass substrate) is set in the above range. And the formula
In the ranges (1) and (3), the relationship between the gas pressure (P) and the thickness (X) of the glass substrate or the thickness (Y) of the dielectric film is determined by determining whether uniform surface light emission can be obtained. As a criterion, the preferred range was recursively verified, and it was found that the range should be the range of equations (2), (4), and (7).

In the invention according to claim 4 of the present application, which focuses on the surface shape forming the discharge space, an airtight discharge space is formed inside the front glass substrate and the back glass substrate in a state where the front glass substrate and the rear glass substrate are combined. In a flat fluorescent lamp in which a phosphor film is formed directly on the inner surface of the front glass substrate and the back glass substrate or via a dielectric film, at least one of the surfaces facing the discharge space has a light emitting spot moved. A number of protrusions are formed for blocking, and the height of the protrusions is H (m
m), the distance between the protrusions is L (mm), and the height of the discharge space is D.
(Mm), the configuration was such that the following expressions (3) and (4) were satisfied. 0.1 ≦ H ≦ 0.5 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (8) 0.8 ≦ D ≦ 2.0 ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ (9) 0.5H ≦ L ≦ D ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (10)

The diameter of the discharge spot is about 1 mm, and by satisfying the above equations (8), (9) and (10), the movement of the discharge spot is suppressed.

In the invention according to claim 5 of the present invention, which focuses on the surface shape forming the discharge space, an airtight discharge space is formed inside the front glass substrate and the back glass substrate in a state where the front glass substrate and the rear glass substrate are combined. In a flat fluorescent lamp in which a phosphor film is formed directly on the inner surface of the front glass substrate and the back glass substrate or via a dielectric film, at least one of the surfaces facing the discharge space has a light emitting spot moved. The configuration is such that a partition wall for blocking is formed. With such a configuration, the movement of the discharge spot is suppressed as in the above case.

Incidentally, as the above-mentioned partition, particles may be arranged in the discharge space in addition to the lattice shape or the like. In this case, it is possible to form a phosphor film on the particle surface. With such a configuration, the movement of the discharge spot is suppressed as in the above case.

The connection between the electrode and the lead terminal is not limited to a resistance connection in which the lead terminal is directly joined to the electrode.
Capacitive coupling may be used.

Further, xenon gas (X
e) When using a single substance or a mixture of xenon gas, Xe is adsorbed on Na eluted on the surface of the glass substrate, and the dielectric constant of the glass substrate itself changes with time.
The surface resistance of the glass substrate decreases. Therefore, as described in claim 8, it is preferable to replace Na ions with K ions on at least the surface of the glass substrate on the discharge space side.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a cross-sectional view of the flat fluorescent lamp according to the present invention, FIG. 2 is a plan view of the flat fluorescent lamp, and FIG. 3 is a view showing another embodiment in which the surface of the phosphor film has an uneven shape. In the flat fluorescent lamp, an airtight discharge space S is formed inside by combining the front glass substrate 1 and the rear glass substrate 2 and sealing them with a low-melting glass frit.

In this embodiment, both the front glass substrate 1 and the rear glass substrate 2 are made of soda-lime glass of 3.2 mm, and particularly, the rear glass substrate 2 is integrally formed in a tray shape. Plane size is 170mm
× 105 mm × 3.2 mm soda lime glass.

A phosphor film 3 is formed on a surface of the front glass substrate 1 facing the discharge space S, and a transparent front electrode 4 is formed on the outer surface. The front electrode 4 is formed, for example, by depositing an ITO film by an evaporation method. The front electrode 4
Has a sheet resistance of 150 kΩ / mm ² . If the sheet resistance exceeds 200 kΩ / mm ² , the light-emitting spot is easily recognized visually, so that the sheet resistance is 200 kΩ / mm ^2.
It is preferable to be Ω / mm ² or less.

A phosphor film 5 similar to that described above is formed on the surface of the back glass substrate 2 facing the discharge space S, and a back electrode 6 made of molybdenum is formed on the outer surface. An AC pulse voltage having a frequency of 30 kHz and a peak voltage of 3 kV is applied to the electrode 6 via a lead terminal 7. Although the shape of the lead terminal 7 is along the three sides of the glass substrate in plan view, it may be a rectangular shape along the entire circumference of the glass substrate.

On the other hand, in the discharge space S, Xe 20%, Ar
A gas having a mixing ratio of 80% is sealed so as to have a total pressure of 66 kPa, and the gap of the discharge space S is 1.5 mm. This gap is preferably set to 1.1 mm to 1.8 mm. If it is less than 1.1 mm, the brightness is reduced to 1.8.
If the thickness exceeds mm, the gas filling pressure must be equal to or higher than the atmospheric pressure in order to increase the luminous efficiency, so that leakage is likely to occur.

When the thickness of the front glass substrate 1 and the rear glass substrate 2 is changed in the range of 1.0 mm to 3.5 mm and the gas filling pressure (P) is further changed, 1.6 logX + 5.9. × 10 ⁴ ≦ P ≦ 1.6 logX + 1
When 1.5 × 10 ⁴ was satisfied, uniform surface light emission was obtained even when the luminance was lowered.

FIG. 3 is a view showing another embodiment in which the surfaces of the phosphor films 3 and 5 are made uneven, and the projections 3a and 5a are formed on the phosphor films 3 and 5 as in this embodiment. As a result, the light emission spot does not move and falls within a predetermined range, so that stable light emission without flicker can be obtained. In order to obtain such an effect, when the height of the projections is H (mm), the interval between the projections is L (mm), and the height of the discharge space is D (mm), 0.1 It has been found that it is preferable to satisfy ≦ H ≦ 0.5, 0.8 ≦ D ≦ 2.0 and 0.5H ≦ L ≦ D.

FIGS. 4 to 6 show another embodiment for suppressing the movement (fluctuation) of the light emitting spot. In the embodiment shown in FIG.
The partition 8 is provided on the surface facing the, and the discharge space S is divided into a number of small spaces S1 so that the light emitting spot is held in each of the small spaces S1. Means for forming the partition wall 7 include press molding, dry etching using plasma, sol-gel method, and ablation by laser beam irradiation (a phenomenon similar to evaporation).

In the illustrated example, the phosphor film 5 is formed on the entire surface of the small space S1.
The phosphor film 5 may be formed only on the bottom surface of the front glass 1, or a partition may be provided on the surface of the front glass 1.

In the embodiment shown in FIG. 5, a large number of concave surfaces 9 are formed on the surface of the rear glass substrate 2 facing the discharge space S, and the movement of the light emitting spot (wobbling) is suppressed by the concave surfaces 9. I am trying to do it. As a method for forming such a concave surface 9, for example, wet etching using hydrofluoric acid can be considered. A concave surface can be formed on the surface of the front glass substrate 1 facing the discharge space S, but a concave surface is particularly formed on the surface of the rear glass substrate 2 if only the movement (staggering) of the light emitting spot is suppressed. Thereby, the effect of improving the luminance by reflection can be expected.

In the embodiment shown in FIG. 6, a large number of fine particles 10 are provided in the discharge space S, and the fine particles 10 obstruct the movement (fluctuation) of the light emitting spot. Particularly, as shown in the drawing, the luminance can be improved by forming the phosphor 10a also on the surface of the fine particles 10.

FIG. 7 is a sectional view showing another embodiment in which both the front electrode and the back electrode are provided inside, and FIG. 8 is an enlarged sectional view of a main part of the flat fluorescent lamp shown in FIG. A transparent front electrode 4 is formed on the surface of the front glass substrate 1 facing the discharge space S, a dielectric layer 11 is provided on the surface of the front electrode 4, and the phosphor film 3 is formed on the dielectric layer 11. And a part of the front electrode 4 is drawn out to the outside and the lead terminal 7 is connected. The lead-out portion of the front electrode 4 is sealed with a low-melting glass frit similarly to the bonding portion between the front glass substrate 1 and the rear glass substrate 2.

A back electrode 4 is formed on the surface of the back glass substrate 2 facing the discharge space S, a dielectric layer 12 is provided on the surface of the back electrode 4, and a phosphor film 5 is formed on the dielectric layer 12. And a conductor film 13 on the outer surface of the rear glass substrate 2.
Is formed, and the lead terminal 7 is connected to the conductor film 13 so as to generate a discharge by capacitive coupling.

Here, the dielectric layers 11 and 12 are formed by applying water glass and then heating to 500 ° C., and have a thickness of about 200 μm.

In this embodiment, as shown in FIG. 8, irregularities are formed on the dielectric layer 11 to prevent the movement of the light emitting spot, and the irregularities are formed on the surface of the dielectric layer 11. The irregularities are reflected on the phosphor film 3 as they are.

FIG. 9 is a sectional view showing another embodiment in which a front electrode is provided outside and a back electrode is provided inside. This embodiment has a structure in which the above embodiments are combined. In this case, instead of capacitive coupling, a hole is formed in the rear glass substrate 2, and the lead terminal 7 is directly connected to the rear electrode 6 through this hole. After the lead terminal 7 is inserted,
The hole is hermetically closed with a low melting glass frit.

[0032]

As described above, according to the flat fluorescent lamp according to the present invention, the gas pressure sealed in the discharge space and the dielectric layer or glass substrate located between the electrode and the phosphor film can be used. Since a certain relationship between the thickness and the thickness is satisfied, even when the luminance is reduced at night or the like, uniform light emission is performed in the plane.

Further, according to the flat fluorescent lamp of the present invention, the movement of the light emitting spot can be suppressed by providing unevenness on the light emitting surface or dividing the discharge space into a number of small spaces communicating with each other. Therefore, uniform light emission is performed without generating flicker.

[Brief description of the drawings]

FIG. 1 is a sectional view of a flat fluorescent lamp according to the present invention.

FIG. 2 is a plan view of the flat fluorescent lamp.

FIG. 3 is a diagram showing another embodiment in which the surface of the phosphor film is made uneven.

FIG. 4 is a sectional view showing another embodiment in which the surface shape of the glass substrate is changed.

FIG. 5 is a sectional view showing another embodiment in which the surface shape of the glass substrate is changed.

FIG. 6 is a sectional view showing another embodiment in which fine particles are interposed between glass substrates.

FIG. 7 is a sectional view showing another embodiment in which both the front electrode and the back electrode are provided inside.

FIG. 8 is an enlarged sectional view of a main part of the flat fluorescent lamp shown in FIG. 7;

FIG. 9 is a sectional view showing another embodiment in which a front electrode is provided on the outside and a back electrode is provided on the inside;

[Explanation of symbols]

1: front glass substrate, 2: rear glass substrate, 3, 5, 1
0a: phosphor film, 3a, 5a: convex portion, 4: front electrode, 6
... Back electrode, 7 ... Lead terminal, 8 ... Partition, 9 ... Concave surface, 1
0: fine particles, S: discharge space, S1: small space.

Claims (8)

[Claims] In a flat fluorescent lamp in which an airtight discharge space is formed in a state where a front glass substrate and a rear glass substrate are combined, a phosphor film is formed on inner surfaces of the front glass substrate and the rear glass substrate. A transparent front electrode is formed on the outer surface of the front glass substrate, a rear electrode is formed on the outer surface of the rear glass substrate, and the pressure of the gas in the discharge space is set to P (Pa). The thickness of X (m
m), a flat fluorescent lamp satisfying the following expressions (1) and (2). 1.0 ≦ X ≦ 3.5 (1) (1.6logX + 5.9) × 10 ⁴ ≦ P ≦ (1.6logX + 11.5) × 10 ⁴・ ・ ・ ・ ・ (2) 2. A flat fluorescent lamp in which an airtight discharge space is formed inside a front glass substrate and a rear glass substrate in a state where the front glass substrate and the rear glass substrate are combined, wherein a transparent front electrode and a dielectric material are provided on the inner surface of the front glass substrate. A film and a phosphor film are sequentially formed, and a back electrode, a dielectric film, and a phosphor film are sequentially formed on the inner surface of the back glass substrate. Further, the gas pressure of the discharge space is set to P (Pa), A flat fluorescent lamp characterized by satisfying the following expressions (3) and (4) when the thickness of the dielectric film is Y (mm). 10 × 10 ⁻³ ≦ Y ≦ 1.3 ・ ・ ・ ・ ・ ・ ・ ・ ・ (3) (1.6logY + 5.9) × 10 ⁴ ≦ P ≦ (1.6logY + 11.5) × 10 ⁴・ ・ ・ ・ ・ (4) 3. A flat fluorescent lamp in which an airtight discharge space is formed in a state in which a front glass substrate and a rear glass substrate are combined, wherein one of the front glass substrate and the rear glass substrate is formed of a glass substrate. A phosphor film is directly formed on the inner surface and an electrode is formed on the outer surface. An electrode, a dielectric film and a phosphor are formed on the inner surface of the other glass substrate of the front glass substrate or the back glass substrate. Films are sequentially formed, and the gas pressure in the discharge space is increased to P
(Pa), when the thickness of one glass substrate is X (mm) and the thickness of the dielectric film is Y (mm), the following equations (5) to (5)
A flat fluorescent lamp characterized by satisfying (7). 1.0 ≦ X ≦ 3.5 (5) 10 × 10 ^-3 ≦ Y ≦ 1.3・ ・ ・ ・ ・ ・ ・ (6) (1.6logY + 5.9) × 10 ⁴ ≦ P ≦ (1.6logX + 11.5) × 10 ⁴・ ・ ・ ・ ・ (7) 4. An airtight discharge space is formed inside the front glass substrate and the rear glass substrate in a state where the front glass substrate and the rear glass substrate are combined, and a phosphor film is formed directly or on a dielectric film on inner surfaces of the front glass substrate and the rear glass substrate. In the flat-type fluorescent lamp formed through the intervening surface, at least one of the surfaces facing the discharge space is provided with a large number of convex portions for preventing the movement of the light emitting spot, and the height of the convex portions is set to H (mm). ), The distance between the protrusions is L (mm), and the height of the discharge space is D (mm),
A flat fluorescent lamp characterized by satisfying the following expressions (8) to (10). 0.1 ≦ H ≦ 0.5 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (8) 0.8 ≦ D ≦ 2.0 ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ (9) 0.5H ≦ L ≦ D ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (10) 5. An airtight discharge space is formed inside the front glass substrate and the rear glass substrate in a state where the front glass substrate and the rear glass substrate are combined, and a phosphor film is directly or a dielectric film formed on inner surfaces of the front glass substrate and the rear glass substrate. A flat fluorescent lamp, wherein a partition wall for preventing movement of a light emitting spot is formed on at least one of the surfaces facing the discharge space. 6. The flat fluorescent lamp according to claim 5, wherein the partition walls are made of particles. 7. The flat fluorescent lamp according to claim 1, wherein a front electrode formed on the front glass substrate or a rear electrode formed on the rear glass substrate is formed on a discharge space side. A flat fluorescent lamp, wherein an electrode formed on a discharge space side and a lead terminal for supplying power to the electrode are capacitively coupled. 8. The flat fluorescent lamp according to claim 1, wherein at least xenon is sealed in the discharge space, and Na ions are K ions on at least a surface of the glass substrate on the discharge space side. A flat fluorescent lamp characterized by being replaced with: